手绘运动学机构示意图识别及运动过程模拟

Handwritten sketch recognition of kinematic diagram and simulation of motion

目的为了解决手绘运动学示意图对辅助学习的局限性,以及现有物理辅助教学软件只能模拟系统设定机构的局限性,提出了一种对手绘运动学机构示意图进行识别,并实现其运动过程模拟的方法。方法首先提取笔画的几何特征进行笔画识别,得到笔画类型,然后根据构件笔画组成列表及笔画间相对关系,进行构件的匹配识别,再根据用户意图,识别构件间位置约束关系,自动矫正机构示意图中构件的相对位置,最后通过2维物理引擎,实现机构的运动过程模拟。结果实现了对运动学教学中常见的16种构件的识别,和构件中常用的7种图元的识别,识别准确率分别为93.25%、94%。结论实验结果表明,该方法可在对手写运动学构件符号以及构件间的约束关系进行正确的识别和矫正的基础上,实现对整个运动机构的识别,以及对机构运动过程的模拟。

Objective The rapid popularization of hardware devices,such as intelligent terminals,has made makes it convenient to interact with the computer,thereby enabling people to initially enjoy the advantages of natural human-computer interaction.The increase in successful applications of many handwritten recognition systems has made sketch-based interactive technology with sketch and handwritten recognition a major research area.Teaching through computer aids has become the most commonly used teaching method and can effectively help students understand knowledge in the textbook better.Kinematics is a branch of theoretical mechanics and is the basis of various engineering disciplines.In kinematics courses,teachers usually use a handwritten or force diagram on the blackboard to help students understand the abstract principles or formulas.In the teaching process,students study most of the movements and the results through imagination;thus,they cannot intuitively feel and understand theoretical knowledge.Therefore,the abstract nature of theoretical knowledge and the difficulty in concluding the diagram lead to learning difficulties.At present,many achievements in the use of computer aids in physics courses have been made,but most of these achievements are based on images,videos,and other materials.Thus,teachers can only teach through display,which lacks interaction,and the teaching content and form are inflexible.Modern computer technology should be applied to solve the problems encountered in physics teaching.On the basis of the traditional teaching form,the advantages of modern computer technology should be fully utilized to construct an intuitive and flexible education model,which not only can help teachers explain the abstract physics theory but also can provide students with a flexible and active learning platform.Therefore,we provide a method to recognize the mechanism of the handwritten kinematics diagram and simulate the motion of the mechanism.Method On the basis of the analysis on the common mechanisms in the teaching of kinematics,this study summarizes 16 common links.On the basis of the analysis on these links,we divide the constituent primitives of the link diagram into seven categories,namely,straight line,broken line,circle,point,arc,rectangle,and triangle.Then,we propose a recognition algorithm for links based on the recognition of the handwritten primitives.In the process of link drawing,each stroke is recognized and the types of strokes are recorded.First,the stroke geometry is extracted and used in stroke recognition to identify the type of stroke.From the analysis on the users＇ habit of drawing the diagram,we can summarize the link with the composition of and the relationship among the primitives to establish a link library.When the link drawing is finished,we can derive a list of the types of strokes.Then,we compose the list of the types of strokes and the relative positions between strokes to recognize the links through matching with the link library.This study establishes the constraint relationship,which conforms to the users＇ intention and implements position correction to the link in the organization diagram.Finally,the simulation of the movement process of the mechanism is achieved on the basis of a 2D physics engine.Result The recognition of 16 types of common links in kinematics teaching was achieved.The recognition accuracy rate of most of the links was 90% or more,among which the recognition accuracy rate of ball,rod,and line reached 100%.Meanwhile,the average accuracy rate of recognition was 93.25%.Moreover,the average accuracy rate of recognition of seven types of primitives commonly used in the links was 94%.Conclusion This study summarizes 16 types of links used in the teaching of kinematics,analyzes the positional relationship between the links,and determines the position constraint relationship among the links.According to the elements of the links and the relative relationship between the primitives,we design a link library for the kinematic mechanism diagram.In this study,we propose a link recognition method based on primitive recognition,and this method can be used to recognize the links by matching the composition of and the relationship among the primitives.The relative position and connection relationship of the primitives in the link are calculated and matched with the link library.On the basis of the position constraint relationship of the links in the schematic of the mechanism,the attribute parameters of the position constraints in each link are analyzed and the position correction rules between the links are designed.Position correction is achieved for the users＇ handwritten input.Experimental results show that the method can recognize the handwritten kinematic links and correct the constraint relationship between these links.By correcting the position of the links,we obtain the motion diagram of the mechanism that conforms to the users＇ intention.In addition,we design the simulation platform of the motion process and simulate the movement process.This method exhibits high recognition rate for any kinematic link inputted by different users in the sample database and supports the user-defined combination of links to form the personalized organization and simulate the movement process.